Integrated circuits (IC's) are known to include a substrate, one or more dielectric layers on the substrate, and one or more metal layers supported by a corresponding dielectric layer. The metal layers are fabricated in such a way to produce on-chip components such as resistors, transistors, capacitors, inductors, et cetera. How an on-chip component is fabricated and the physical limits placed on on-chip components are dictated by the technology used and foundry rules governing such technology.
For example, CMOS technology is readily used for cost effective integrated circuits. Foundries that manufacture CMOS integrated circuits provide rules governing the number of dielectric layers, number of metal layers, metal track sizes, spacing between metal tracks, angular bends of metal tracks, and other aspects of integrated circuit production.
While CMOS technology and the corresponding foundry rules allow on-chip inductors to be created, the quality factor (i.e., the measure of a component's ability to produce a large output at a resident frequency and selectivity of the component) is limited to a value of 5-10. As is known, a circular trace pattern for an on-chip inductor theoretically has a greater Q factor than a square or rectangular trace pattern of similar inductance, but has a larger IC footprint and violates foundry rules. As such, circular on-chip inductors are not used.
To emulate the benefits of a circular on-chip inductor, while maintaining compliance with foundry rules, many integrated circuit designers use an octagonal inductor. However, an octagonal inductor is larger than a similar trace length square or rectangular inductor. As such, IC designers choose between larger octagonal inductors with a higher Q factor and smaller square or rectangular inductors with a lower Q factor. In some instances, an octagonal inductor is impractical due to its size and yet a square or rectangular on-chip inductor is impractical due to its low quality factor. And, in all instances, smaller on-chip inductors with similar performance characteristics are preferred over larger on-chip inductors.
Therefore, a need exists for a high quality factor rectangular and/or square on-chip inductor.